1. Field of the Invention
The present invention relates to a semiconductor device with a deep trench structure and, more particularly, to a semiconductor device with a deep trench structure for effectively isolating heavily doped wells of neighboring elements from each other at a high operating voltage.
2. Background of the Related Art
As integrated circuits having various functions coexist in the same product because of high integration of semiconductor circuits, a multi-voltage/current driving high voltage transistor is required.
A thin film transistor-liquid crystal display (TFT-LCD) includes a driving circuit and a control circuit. The control circuit has a logic circuit operating at 5V and the driving circuit has a high voltage transistor operating at higher than 30V, and thus the TFT-LCD cannot be manufactured using a standard complementary metal oxide semiconductor (CMOS) process. Furthermore, when a high voltage device manufacturing process is applied to the TFT-LCD, power consumption of the control circuit and the size of the TFT-LCD increase.
To solve these problems, there is proposed a method of adding a mask process and an ion implantation process to a 1.2 μm logic manufacturing process to easily control voltage and current levels without changing characteristics of logic elements.
Meanwhile, a conventional high voltage device employs deep wells in order to endure a high voltage. In this case, it is difficult to isolate neighboring wells from each other as an operating voltage of the high voltage element increases.
Referring to FIG. 1, drift regions 1 are formed in a substrate having a high voltage well HNW formed therein and a gate oxide 2 and a gate electrode 3 are formed thereon. Source and drain regions 5 are respectively formed in the drift regions 1 having the gate electrode 3 formed therebetween and bulk ion implanted regions 6 are formed in the high voltage well HNW. The source and drain regions 5 are respectively isolated from the bulk ion implanted regions 6 according to a narrow isolation layer 4.
Here, although the source and drain regions 5 can be respectively isolated from the bulk ion implanted regions 6 using the narrow isolation layer 4, a wide isolation layer 7 should be formed in order to isolate the high voltage well HNW because the isolation layer 7 has a shallow trench structure in a high voltage device having a high operating voltage, as illustrated in FIG. 1. This increase the size of the high voltage device, and thus the high voltage device is not suitable for a driving IC.
That is, the increase in the size of the high voltage device causes an increase in the device cost and deterioration of integration, and thus the high voltage device is not suitable to be used as a driving IC because current devices require a small size, high integration and low cost.